JPH01215307A - Hollow yarn membrane made of aromatic polysulfone and production thereof - Google Patents

Abstract

PURPOSE:To obtain a hollow yarn membrane having high water permeability required for ultrafiltration but preventing the permeation of gas from the outer surface owing to the dense outer surface structure by regulating the water permeability of a hollow yarn membrane in water under pressure to a specified value or above and the gas permeability in air under pressure to a specified value or below. CONSTITUTION:A spinning soln. prepd. from polysulfone, a solvent such as N-methyl-2-pyrrolidone or 2-pyrrolidone and additives such as polyethylene glycol is spun into hollow yarn by dry-wet spinning with a tube-in-orifice type nozzle. At this time, an internal solidifying liq. such as an aq. soln. of polyethylene glycol and an external solidifying liq. such as warm water are used and the temp. of the ejected spinning soln. is made higher than the temps. of the solidifying baths. Thus, a hollow yarn membrane made of arom. polysulfone and not having pores of >=0.2mum diameter in the outer surface is obtd. The water permeability of the membrane in water under 1kg/cm<2> pressure is >=600l/m<2>.hr and the gas permeability in air under 1kg/cm<2> pressure is <=0.01ml/m<2>.hr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel hollow fiber separation membrane made of a polysulfone polymer and a method for producing the same.

(Prior art and problems) Polysulfone, known as engineering plastics, has excellent mechanical properties, heat resistance, and chemical resistance, so it is used in household products and medical equipment fields. Widely used in precision parts field.

Since such polysulfone can be easily spun into hollow fibers, it can be used as a hollow fiber separation membrane for gas and liquid separation. In particular, it is extremely useful as an ultrafiltration membrane under high temperature, strongly acidic or strongly alkaline conditions.

As a method for manufacturing such a polysulfone hollow fiber separation membrane, for example, Japanese Patent Application Laid-Open No. 54-145379.56-15
2704.58-8504.58-132112.58
-156018.59-58040.59-58042
．． 59-62311, 59-189903.60-17
2312.60-222112.61-11110.6
1-28409.61 to 42307.61-93801
The method described in is known. By these methods, polysulfone hollow fiber membranes with different membrane structures and different membrane performances can be produced, but the surface structure has pores with a pore size of about 50 λ to 10 μm on the inner or outer surface. be. In addition, the pure water permeation rate of these hollow fiber membranes is 100-1200Q/m in pressure measurement.
"・hr-kg/cm" (inner surface area standard), in external pressure measurement, 50 to 700Q/m"・hr-kg/
c+++'' (based on external surface area), a hollow fiber membrane with high water permeability is desired in order to improve productivity.

However, in the polysulfone hollow fiber membrane obtained by the above manufacturing method, as the water permeability improves, the pore diameter of the membrane surface increases, and the pore size of the membrane surface increases by 6OOC/m'-
Hollow fiber membranes with high water permeability of hr -kg/cm or more usually have pores with a pore diameter of several μm or more on the outer surface.
Although a highly water permeable hollow fiber membrane of over 00OOC/m''・hr-kg/Cm! can be obtained, the mechanical strength of the membrane is low due to the use of a spinning dope with low polymer density, and the internal and external The structure has large pores with a diameter of 1 μm on the surface.

In general, in wet-dry spinning, in which the spinning stock solution is discharged from a tube-in-orifice nozzle through a dry zone into a coagulation bath, high water permeability can be achieved by increasing the temperature of the coagulation bath or by increasing the temperature and humidity of the dry zone atmosphere. Although this method is known as a method for obtaining hollow fiber membranes, even when this method is used, the result is that the inner or outer surface has large pores, and the fractionation performance of the membrane often changes.

In addition, the presence or absence of pinholes can be inspected by pressurizing the outer surface of the hollow fiber with air or gas such as nitrogen in water, but if there are large pores on the outer surface, the outer surface will be inspected regardless of the pinhole. Another problem is that the gas that has passed through the hollow fiber is discharged from the end face of the hollow fiber through its thick wall, making it difficult to determine the presence or absence of pinholes. Therefore, it is most desirable for a highly water-permeable membrane to have a large number of small pores on the membrane surface.

Therefore, the present invention is limited? In particular, in the present invention, the hollow fiber membrane is characterized in that it has the highly required high water permeability, has a dense structure on the outer surface, and substantially does not allow gas to pass through the outer surface. When passing through the limit of about 10,000, the pure water permeation rate measured using an external pressure method is 60,000 yen.
0i2/m'-hr-kg/cm'' (based on outer surface area)
The purpose of the present invention is to satisfy the above conditions in the hollow fiber membrane made of aromatic polysulfone.

(Means for Solving the Problems) As a result of intensive study and research in order to solve the above problems, the present inventors found that in hollow fiber membranes that do not have pores with a pore diameter of 0.2 μm or more on the outer surface, The gas permeation rate is several kg/c.
We discovered that it is almost impossible to apply a pressure of
We have arrived at the present invention.

That is, in the present invention, under a pressure of 1 kg/cm, the water permeability is 600 ff/m"・hr or more when pressurized with an iceberg, and the air permeability is 0.01 m12/m when pressurized in air.
The purpose of the present invention is to provide an aromatic polysulfone hollow fiber membrane characterized in that the heating time is less than -hr, and a method for producing the same.

The polysulfone polymer used in the present invention refers to polysulfone represented by the following structural formula.

CH, O, are integers The composition of the spinning stock solution is not particularly limited as long as it can be maintained in a uniformly dissolved state, and may include the above polymer and a solvent that dissolves it, or a non-solvent or various additives that do not dissolve the above polymer, etc. A stock solution prepared from the above can be used.

As the solvent for dissolving the above polymer, 2-pyrrolidone,
N-methyl-2-pyrrolidone, dimethylformamide,
Dimethylacetamide and tetramethylurea are commonly used. In addition, examples of non-solvents and additives that do not dissolve the above polymers include cyclic ethers such as dioxane and tetrahydrofuran, lower aliphatic ketones such as acetone and methyl ethyl ketone, ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol,
Aliphatic polyhydric alcohols such as glycerin, dimethyl sulfoxide, water, etc. are generally used, but in addition to these, organic compounds such as aliphatic ethers, carboxylic acids, amines, and various organic or inorganic salts can also be used.
- The polymer concentration in the spinning dope is preferably 5 to 35% by weight, particularly preferably 10 to 30% by weight. If the polymer concentration in the stock solution is less than 5% by weight, the mechanical strength of the hollow fiber membrane obtained will decrease significantly, which is undesirable.
If it exceeds 5% by weight, the viscosity of the solution increases, making it difficult to handle, and at the same time, the water permeation rate of the resulting hollow fiber membrane decreases, which is not preferable.

According to the method of the present invention, the spinning stock solution prepared as described above is discharged into an aqueous solution using a tube-in-orifice type nozzle, and the spinning conditions at this time are extremely important in the present invention. Although it is possible to obtain hollow fibers that do not have pores with a pore size of 0.2 μm or more on the outer surface using either the wet-dry or wet-spinning method, wet-dry spinning is most desirable in order to achieve a higher water permeation rate.

Internal and external coagulation liquids include water or methanol;
Lower aliphatic alcohols such as ethanol, propatool and butanol, the above-mentioned cyclic ethers, lower aliphatic ketones, aliphatic polyhydric alcohols, etc. are used alone or in combination of two or more, and various organic solvents and other It is also possible to use additives. Further, the temperature of the external coagulation liquid is preferably 40° C. or higher in order to obtain a highly water permeable hollow fiber membrane. Further, it is essential that the temperature of the spinning stock solution discharged from the nozzle is higher than the temperature of the external coagulation liquid. If the temperature of the stock solution is lower than the temperature of the external coagulation liquid, the pores on the outer surface of the hollow fibers will grow large, which is not preferable.

In dry-wet spinning, the temperature of the dry part atmosphere is preferably 40°C or higher and the relative humidity is preferably 80% or higher in order to increase water permeability.
At this time, the residence time in the air of the spinning stock solution discharged from the nozzle must be such that the temperature of the stock solution does not drop to become lower than the temperature of the external coagulation tank. The temperature of the dry part atmosphere is 40℃
If the relative humidity is less than 80%, the temperature of the spinning stock solution decreases during air retention, and the water permeation rate of the resulting hollow fiber membrane decreases, which is not preferable. In addition, even if the temperature of the dry part atmosphere is 40°C or higher and the relative humidity is 80% or higher, if the residence time in the air of the spinning dope discharged from the nozzle exceeds 0.2 seconds, pores on the outer surface of the hollow fibers It is not desirable because it grows large.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these in any way. Note that in the Examples and Comparative Examples below, pure water permeation rates are measured, but these are all values calculated based on the external surface area by external pressure measurement.

Example 1 Polysulfone (manufactured by UCC, needle polysulfone P)
-1700) 20 parts by weight, N-methyl-2 as a solvent
- 40 parts by weight of pyrrolidone, 20 parts by weight of 2-pyrrolidone,
A spinning stock solution uniformly prepared from 20 parts by weight of polyethylene glycol (PEG 100G) having an average molecular fi of 1000 as an additive was discharged into water from a tube-in-orifice nozzle to spin hollow fibers.

The internal coagulation liquid is 75% polyethylene glycol (
P E G 200) Aqueous solution, 60 as external coagulation liquid
℃ warm water was used. The temperature of the spinning dope discharged from the nozzle is 65°C, the residence time in the air is 0.15 seconds, the temperature of the dry part atmosphere is 42°C, the relative humidity is 95%, and the spinning speed is 20°C.
m/sin. Next, the obtained hollow fibers were washed with 60° C. warm water until the solvent was completely removed.

The hollow fiber membrane obtained in this way has a weight of l kg/cn+2
The water permeability rate was measured by passing purified water (pure water) at a water pressure of 760I2/m"・hr -kg/cm"
and conalbumin (protein: molecule ffi 87
000) had a transmittance of 23%. Also l kg/c
m” The amount of air permeation from the outer surface under pressure is 7X10-
3IIIQ/I11″·hr-kg/cm” or less.

Next, after fabricating a module with a total external pressure r excess using this hollow fiber membrane, it was immersed in water and the outer surface of the fiber was heated to 2 kg/c.
When the sample was inspected for the presence of pinholes by pressurizing it with nitrogen gas, no bubbles were observed at all from the ends of the hollow fibers, and it was confirmed that there were no pinholes.

Comparative Example 1 Example! Prepare the same spinning stock solution as above, and set the air residence time to 0.
Spinning was carried out under the same conditions as in Example 1 except that the spinning time was 3 seconds.

The pure water permeability rate of the obtained hollow fiber was 750Q/ff11h.
r・kg/cn+", and the conalbumin permeability is 1
It was 7%. Also, the amount of air permeation from the outer surface under 1 kg/cm'' pressure is 90 mff/m''・hr-kg/
cI11! That was it.

Next, when a pinhole inspection similar to that in Example 1 was performed, a large number of minute bubbles were generated from the end face of the hollow fiber, and it was difficult to determine whether these bubbles were generated in the hollow part of the hollow fiber or in the thick part. was almost impossible to distinguish.

Comparative Example 2 The same spinning stock solution as in Example 1 was prepared, and spinning was performed under the same conditions as in Example 1, except that the temperature of the stock solution when discharged from the nozzle was 58°C.

The pure water permeability rate of the obtained hollow fiber was 650ρ/m”-hr
・kg/cm” and conalbumin permeability is 17%
Met. Also, the amount of air permeation from the outer surface under 1 kg/cm" pressure is 50 m12/I11!・hr-kg/
It was larger than a cm parrot.

Next, when a pinhole inspection similar to that in Example 1 was performed, many minute bubbles were generated from the end face of the hollow fiber, and it was unclear whether these bubbles were generated in the hollow portion of the hollow fiber or in the thick portion. was almost impossible to distinguish.

(Effects of the Invention) As explained above, the polysulfone-based polymer hollow fiber membrane obtained by the production method of the present invention has extremely high water permeability, and at the same time, pinhole inspection is performed after modularization. It facilitates

Patent and patent applicant: Daicel Chemical Industries, Ltd.-8.

Claims (4)

[Claims] (1) Under a pressure of 1 kg/cm^2, the water permeability is 600 l/m^2 hr or more when pressurized in water, and the air permeability is 0.01 ml/m^2 when pressurized in air.・An aromatic polysulfone hollow fiber membrane characterized by a hr or less. (2) The aromatic polysulfone hollow fiber membrane according to claim 1, characterized in that no pores with a pore diameter of 0.2 μm or more are present on the outer surface. (3) In dry-wet spinning in which aromatic polysulfone spinning dope is discharged from a tube-in-orifice type nozzle through a dry section into a coagulation bath, the temperature of the spinning dope is higher than the temperature of the coagulation bath. A method for producing hollow fiber membranes made of aromatic polysulfone. (4) The method for producing a hollow fiber membrane made of aromatic polysulfone according to claim 3, wherein the aromatic polysulfone is a polysulfone consisting of a repeating unit represented by ▲a numerical formula, a chemical formula, a table, etc.▼.